Cast ferrous nitrided article



l atented May 2, 1333 hairs. srnras 01F SZPGKFIELD, MASSACHUSETTS, ASSIG-NOR TO TTQORE DROT ALBERT. W. EI'KQRRTS,

LQEGING 01F SPRINGFIELD, MASSAUSETTS, A QQREQRATION Q15 MAS- SAUEETUSETT 17o Drawing.

This invention relates to a cast ferrous article having a superior wearing surface produced by the so-called nitriding process.

Dificulty has been found in producing a cast iron article having a nitrided surface.

By cast iron I mean an alloy of iron containing from 1.7% to 3.75% of carbon.

The alloy that T particularly am aiming to improve is an iron alloy containing 2.40% w to 2.7 5% of carbon.

T have discovered from experiment and research that this particular alloy can be readily pre ared for the nitriding process by simply a ding about 1% to 2% of zirconium to the molten alloy, it being unnecessary to add any other element except the zirconiurn.

The zirconium is added to the molten iron alloy preferably in the form of ziroconium.

silicate in an amount proper to add 1% to 2% of pure zirconium to the mixture.

After the mixture is formed the same is poured into a mold to form the article.

After this casting has set or cooled, the same is submitted to a nitriding process whereby it is subjected to" free nitrogen which will combine with and nitrate or harden the surface of the article.

By using the particular percent of zirconium specified and practically no other element, if have found that cast iron as above defined can be cheaply and eficiently nitrided.

The article thus produced may be malleableized or heat treated in addition to being 5 nitridized, and machined or ground to exact size or shape.

The cast article thus made has the follow ing advantages. i

l. lit will die cast and the alloing elem merits will not have suficient tiity for oxygen or'anyptherfgas to form any pompound that causes non-metallic inclusion. This is not true. of other alloys used for this A 5 purpose such as those containing aluminum.

lit at be straightened while hot, something .which is desirable as most long cast-- ings leave the mold warped or twisted 3. It can be heat treated in a reasonable time, say two hours, and at a reasonable cost.

is is not true of ordinary .u r; cable iron.

CAST FEEEOUS NTTRKDED AltTEGIE 1 Application filed November 21, W31. Serial No. 576,620. L

f. lit will nitride to a hardness of at least. 600 Vickers brinell. This is only true of very few alloys. I t

5. During nitrogenization the casting will remain stable; that is, the nitriding tempera. ture will not warp it. y

" 6. While the casting will grow while it is being nitrided it will grow uniformly so that the growth can be calculated.

7. The casting will finish with a steel like surface that is, with no free carbon showing. Any free carbon is present only as mmper carbon.

Having thus described my invention, what if claim as new and desire to secure by Letters Patent of the United States, is

1. As a new article of manufacture, a cast ferrous article, substantially freeof alumihum, and containing. from 1.7 percent to 3.75 percent of carbon and one to two percent of zirconium and having its surface hardened by nitriding. p p

2. As a new article of manufacture, a cast ferrous article containing from 1.7 percent to 3.75 percent of carbon and one to two 75 percent of zirconium and substantially no other element, and having its surface hardened by the nitriding process.

3. As a new article of manufacture, a cast iron article, substantiaily free of aluminum and containing one to two percent of zirconium and having its surface hardened by nitriding. i

In testimony whereof l have hereunto affixed my signature.

. ALBERT W. MURTJRLTS. 

